Frama-C-discuss mailing list archives

This page gathers the archives of the old Frama-C-discuss archives, that was hosted by Inria's gforge before its demise at the end of 2020. To search for mails newer than September 2020, please visit the page of the new mailing list on Renater.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Frama-c-discuss] Jessie - problem with an example

Hello Kerstin,

Le mer. 09 sept. 2009 10:31:23 CEST,
"Kerstin Hartig" <kerstin.hartig at> a ?crit :

>     behavior yes:
>       assumes data->a <= data->b + 10; 
>       assigns data->b;
>     ensures data->b <= data->a;
>  */
> void refresh(struct MyData* data)

I guess your issue lies here: there is no post-condition saying that
data->b is positive. We only know that it is less than or equal to
data->a (By the way, your indentation is a bit misleading: the ensures
relates only to the behavior 'yes', not to all behaviors).
It is thus not possible to conclude that data->b is positive in the
main loop after the call to refresh. Remember that function calls are
seen as some kind of black box and that the only things which are known
outside of the function body are the clauses of the contract.

Virgile Prevosto
Ing?nieur-Chercheur, CEA, LIST
Laboratoire de S?ret? des Logiciels
+33/0 1 69 08 71 83